Scouring article and method for making same



Dec. 3, 1963 J.-A. CAMERON SCOURING ARTICLE AND METHOD FOR MAKING SAME Filed Aug. l5, 1961 INVENTOR t John A.Comeron 'SYM-E )mb ATTORNEY United States Patent O 3,112,584 SCOIRING ARTICLE AND METHOD FOR MAKING SAB'IE John A. Cameron, Evanston, Ill., assignor to General Foods Corporation, White Plains, N.Y., a corporation of Delaware Filed Aug. 15, 1961, Ser. No. 131,663 4 Claims. (Cl. 51-185) This invention relates to scouring devices of the type used in the home and in Various industrial areas. More particularly, the invention is concerned with the production of a non-metallic, fibrous scouring article capable of replacing soap and/or detergent-impregnated metal wool pads. The term detergent as it is employed in the specication and accompanying claims is intended to cover synthetic detergents, soaps and other saponaceous materials of varying degrees of surface activity commonly employed in the cleansing art.

Metal wool, .for example so-called steel Wool, has gained wide acceptance for scouring household articles, such as pots and pans. Scouring and polishing pads made of steel wool strands which have been matted or felted together, or intertwined or interwoven into a mass of filaments, are also employed in the industrial field for the removal of old waxes preparatory to reapplication of wax.

Such metal wool pads are noted for their abrasive characteristics and rely upon the relative hardness of the metal for their scouring action. However, metal wool pads suffer from a number of undesirable characteristics. Metal Wool itself is harsh and unpleasant to the touch. Unsightly rusting may occur after several submersions of a pad in water. Moreover, the metal wool can break or splinter and result in slivers of metal entering the skin of the user or being left as a residue on the scoured structure, e.g., a floor, in which event an uneconomic cleanup period is required after scouring.

It has, therefore, long been a desire in the trade to find a replacement for metal wool scouring pads, which replacement is non-metallic and therefore exhibits none of the undesirable characteristics which are inherent in the use of a metal scouring article. Among classes of materials which have been suggested as replacements for metal wool are natural organic fibers, such as entangled filaments of cotton, jute, sisal, Wool or the like. Moreover, synthetic organic fibers, such as nylon and other polyesters, have also been suggested as useful substitutes for metal wool, and an open, high loft, unimpregnated nylon batt is the subject matter of US. Patent No. 2,958,593 to Hoover et al. Both the natural and synthetic organic materials possess one superior characteristic over metal wool in that they have no tendency to rust. Certain of the synthetic fibers are particularly adaptable for utilization in scouring pads, since such compositions are relatively stable at those temperatures likely to be encountered in household and industrial uses of scouring pads. Such synthetics are also resistant to corrosive action of other organic chemicals and are flexible, durable, and compare favorably in cost with metal Wool.

Still another advantage of certain synthetic organic materials such as nylon, polypropylene, vinyl chlorides, rayon acetates, is that they may be formed into monolaments which mono-filaments can be felted into porous, open mats or batts of unusually high loft, springiness and compressibility. Such low density or high voids volume batts lend themselves ideally to a property which is desired in the cleansing art, namely, the ability to absorb water in substantial quantities rapidly and transmit foreign substances of an undesirable character from the working surface whereby such batts can be rinsed free of this matter upon removal from the soiled Surface.

3,112,584 Patented Dec. 3, 1963 Fice More recently, batts of relatively short, interlaced synthetic organic fibers exhibiting a high degree of loft, fiexibility and toughness have become commercially available. For example, the Curlator Corporation, of Rochester, New York, manufacturers of so-called Rando- Webber machines for forming non-woven, fibrous materials, have made possible the production of high-loft structures on a commercial scale. Patent No. 2,890,497, issued lune 16, 1959, to Curlator Corporation on an application filed in the names of Langdon et al., discloses a machine admirably suited for use in preparing highloft batts of synthetic organic fibers.

In order to impart preferred scouring characteristics to batts which may be classified either as high-loft or low-loft structures, it is necessary that finely divided abrasive particles be added to the batt structure. Suitable abrasive mineral grits are silicon carbide, tungsten carbide and fiint fines. Several methods of incorporating abrasive particles in fibers which are interlaced or felted into batt structures suitable for use in scouring pad manufacture are known. One such method is to extrude synthetic filaments of organic material from a molten plastic mass and, while the filaments are still plastic immediately after their extrusion, to propel particles of abrasive matter against them. ln this manner abrasive grits are forced against the plastic filaments, impinge thereagainst and adhere thereto. When the filaments cool to a setting temperature, the particles of abrasive remain imbedded in the filaments and protrude therefrom in position to be utilized for their abrasive characteristics. Such a method is exemplified by Patent No. 2,375,585 to Rimer, issued May 8, 1945. Patent No. 2,334,572 to Melton et al., issued November 16, 1943, discloses a similar method in which a dry, gaseous suspension of abrasive particles and separated fibers are mixed and the resulting material collected in the form of a loosely felted abrasive web. Still another patent which shows a similar method is Patent No. 2,413,551 to England, issued December 31, 19416.

Another general method of incorporating abrasive particles in a fibrous batt is that of spraying a mixture of a liquid adhesive binder having abrasive particles disburscd therein on a surface of a fibrous batt. One such process is disclosed in Patent No. 2,237,199 to Loeffler, issued August 17, 1943. An abrasive pad produced in accordance with such a method will tend to have its greatest concentration of abrasive particles at the one or more surfaces of the batt which are sprayed with the abrasive binder mix. In such a pad, interior portions which have a lower concentration of abrasive particles are apt to retain whatever inherent elasticity and resilience they possess and so give a measure of springiness to the pad as a whole. The abrasive particles may also be adhered to the fibers of the batt by immersing the batt in an adhesive binder mix, in which method there Will be a greater tendency for uniform distribution of the particles throughout the batt.

Many types of adhesive binders may be used to cement together fibers of a batt according to the present invention at areas Where they cross and contact one another, as well as to station abrasive particles on those fibers. In selecting such an adhesive binder the conditions under which the binder is to be used must be taken into consideration. For example, Where the batt containing the adhesive is to be subjected to Water or other fluids at high temperatures, the adhesive binder should be of a type which does not become viscous or pasty at high temperatures, nor should the binder be one which is soluble to any substantial degree in water or the solvent applied to the batt. Then, too, if the adhesive binder dries to a brittle composition, the friction engendered in the use of the final pad may serve to crumble the frangible adhesive and so disrupt the integral structure of the pad.

Among those binders which have been found suitable for use for the purposes of the present scouring article are synthetic resins, e.g., phenolaldehyde resins, butylated urea aldehyde resins, epoxy resins and polyester resins, and modified natural or synthetic rubber such as latex compositions which have been blended with a filler so that they do not become pasty at high temperatures. Among commercial sources of adhesive binders which 'are suitable for use are Shell Chemical Companys Epon `828 which is a liquid epoxy resin, and Hycar Latex 1561, a butadiene-acrylonitrile copolymer latex marketed by B. F. Goodrich Company.

In a method in which the abrasive particles are incorporated in the batt by application thereto in an adhesive binder mix, the adhesive binder adheres somewhat to the filaments along their lengths and primarily serves to unite lilaments at points where they cross and contact each other. Since the binder mix serves to carry the abrasive particles with it, particles of abrasive material will be adhered to the filaments along their lengths and, in particular, at points of contact between filaments. After the adhesive binder has dried and hardened on the filaments, the abrasive particles will be firmly cemented in the binder and secured thereby on the fibers of the batt.

According to the present invention, a fibrous batt, with or without abrasive particles incorporated therein, is produced. Prior art methods of forming such a batt, which has a network of intercommunicating voids, may be utilized, if desired. My scouring article, however, is made from a plurality of sections of such batts. At least one batt section is impregnated with soap or other detergent. The impregnated section is generally located at a central position of the finished scouring article, the unimpregnated batt sections forming the outer plies of the scouring article and having surfaces which directly contact work to be scoured.

As stated, a network of intercommunicating voids is formed in each of the batt sections. In the impregnated section the voids which form the network serve as repositories for detergent globules, which are stored in the voids until contacted with water or some other solvent to bring them to the surface of the scouring article and utilize their cleansing action. In those batt sections which are not impregnated with a detergent, the network of voids permits the passage of detergent emanating from the impregnated batt section through the unimpregnated section to the work-contacting surface of the scouring article.

Concentration of detergent at a central portion of the scouring article and initial omission of detergent from those areas of the article near the work-contacting surfaces of the article provides important advantages. First, it permits the detergent to be metered out in useful quantities without undue dissipation of detergent in amounts in excess of those necessary to cleanse a piece of Work effectively. When detergent is concentrated near the surface of a scouring article, it is rapidly solubilized upon contact with solvent 'and iiows from the scouring article in amounts in excess of those actually required. Pieces of solid detergent may be dislodged by the sudden solubilization of detergent surrounding them and fall from the article. Consequently, much detergent has been found to be Wasted when a scouring article in the form of an open, high loft structure is completely impregnated. The metering effect produced by the concentration of detergent at the center of the scouring article avoids this loss of cleansing power and provides substantially longer scouring pad life per quantity of detergent impregnated therein. 4

A scouring article according to the present invention has a relatively high voids volume, i.e., the total volume of the batt occupied by the void spaces within the batt is large with respect to the batt volume occupied by the fibers, themselves. The void volume may, e.g., be 80 percent of the total volume of a batt from which the scouring article is to be formed. As will be apparent, a

A 4 batt of wettable, synthetic fibers and a high voids volume is elastic and resilient; it will tend to reassume its initial form after it has been compressed and the compression released. The outer, unimpregnated batt sections of the scouring article will, therefore, be resilient and elastic.

The resilience and elasticity of sections of the present scouring article produce a second important advantage over a completely impregnated pad. Compression of these resilient sections presses the air from the voids of those sections. Upon release of the compressive force, the resilient sections reassume their original shape, sucking air into their voids as they do so. As they suck in air, they likewise draw in any detergent in contact with their surfaces and thereby tend to reconcentrate detergent near the center of the scouring pad and to hold some already expended detergent within the pad so that it may be utilized in subsequent scouring operations.

Detergents with which a batt having the abrasive characteristics outlined hereinbefore may be impregnated may be selected from any natural or synthetic detergent which is non-toxic, non-irritating, not rapidlyV soluble and has a melting point substantially above room temperature. The detergent should be non-toxic and non-irritating, of course, so that if any detergent film remains on a pot, pan or other article after a scouring operation, that detergent film will be neither poisonous nor irritating when inverted with food in a subsequent use of the article. In

addition, it should be non-irritating so that the hands of the user are not affected adversely during and after a scouring action employing the pad. Extreme solubility is not a desirable characteristic because it leads to excessive consumption of detergent. If the detergent has a melting point at or below room temperature, it is likely to melt in transit or on the retailers shelf and thus flow from the batt.

Furthermore, a detergent which can be advantageously utilized as the impregnant of a scouring pad according to the present invention is one which is physically and chemically compatible with other detergents with which it is likely to come into contact. It is common, for example, for a scouring pad to be used during or immediately after a dish-Washing operation, in which case the detergent in the scouring pad should be compatible with detergents normally used as dish-washing compositions. Consequently, since most dish-Washing compositions that are now employed include anionic synthetic detergents, use of a soap or cationic detergent in the pad will not be compatible with the dish-washing detergent and will actV adversely on the foam of the dish-washing detergent and destroy a large part of its cleansing power. It is, therefore, preferred that a non-ionic, anionic or amphoteric synthetic detergent be incorporated into the batt to form the present scouring pad.

Among those anionic synthetic detergents which have been found effective as impregnants are alkylaryl sulfonates and lauryl sulfate. A composition commercially available is a sodium salt of alkylaryl sulfonates marketed by Stepan Chemical Company under the trademark DS- 60. Another commercial source of alkylaryl sulfonates is Ultrawet GO-K, produced by Atlantic Rening Company.

Among the non-ionic synthetic detergents which are suitable for use in the present scouring pad are ethoxylated alcohols, acids, phenols, and esters which contain OH groups, in addition to amines, amides, ethoxylated amines and ethoxylated amides. Also desirable are condensation products of an alkylolamine and a number of the group consisting of higher fatty acids and their trylycerides, esters, amides and anhydrides. Among such compositions commercially available is a lauryl dicthanol amide made by Stepan Chemical Company under the trademark P616.

As is well known, certain synthetic detergents, when used together, exhibit synergistic effects which result in markedly superior cleansing action. Thus, a detergent composition which has been found particularly advantageous for use in a scouring pad `of the present invention is one which is composed of about four parts of the sodium salt of alkylaryl sulfonates and about one part of a highly active lauryl diethanol amide.

It should be noted, however, that a wide variety of natural and synthetic detergent materials will be found suitable for use in the present invention, and such materials will readily be determinable by those skilled in the art. Those compositions which have been named hereinbefore as being most advantageous for such use have been selected on the basis of their compatibility with materials with which they may come in contact in the course of household uses. In particular industrial uses it may well be that these detergents will be found more advantageous because they are compatible with other substances with which they are brought in contact in that particular use. Therefore, the selection of a detergent is governed to a large extent by the use to which the batt incorporating it is to be put, the degree of lubricity required, and the cleansing action which must necessarily be obtained.

These and other objects, features, and advantages of the present invention will become more apparent when taken in connection with the following detailed description of a preferred embodiment of the invention and the illustration of that embodiment in the accompanying drawing, which forms a part thereof, and in which:

FIG. l is an exploded, perspective view of a scouring pad according to a preferred embodiment of the invention;

FIG. 2 is a vertical sectional view of the pad of FIG. l on an enlarged scale, and

FIG. 3 is a vertical sectional viewon an enlarged scale of a modified form of pad.

Referring now to the drawing, and in particular to FIGS. 1 and 2 thereof, a scouring article 10 according to this invention is formed from three sections. These are upper section 11, intermediate section 12 and lower section 13. Upper section 11 and lower section 13 are substantially identical in shape and composition. Intermediate section 12 is of different shape and composition. The three batt sections are made integral by means of a suitable adhesive.

Each of sections 11 and 13 is formed from a plurality of synthetic, non-metallic fibers 14 which are disposed throughout each section in a random, three-dimensional arrangement. The fibers 14 are batt sections but are preferably from one-quarter to two inches long. It is of importance that the individual fibers be fixed to other fibers which cross and contact them so as to maintain the unity and shape of each of the batt sections. To maintain such unity a quantity of an adhesive binder is sprayed on or otherwise applied to the batt of loose fibers. In FlGS. l to 3 the binder is seen to be globules 15, which encase at least two fibers 14 at points where they contact or are immediately adjacent each other.

One method of applying adhesive binder to a batt section is to spray the binder on the section. Such spray is directed on at least one surface of the section. It has been found particularly desirable to apply the binder to opposed surfaces of the section, so that all of the fibers of the section adhere to each other and are thus held in a fixed relationship at their points of contact.

Abrasive particles 16 are incorporated into batt sections 11 and 13, particularly at surface portions that are to be utilized to contact the Work to be scoured. According to a preferred method of application of such abrasive particles, the particles are dispersed in the adhesive binder prior to the application of the binder to the pad. If the binder is to be sprayed on work-contacting surfaces of the batt, the abrasive particles will be distributed at such surfaces in locations which are highly desirable, the depth of distribution of the abrasive particles being determined by the force with which the spray is applied to the batt section, the thickness of the section, the void volume of the section and other factors. Abrasive particles 16 do not tend to separate completely from the adhesive binder in which they have been dispersed, but are often partially encased or embedded in a globule of such binder and are stationed on the fibers by means of such globules. Thus abrasive particles are to be found to a large extent at portions where fibers cross and contact one another, since these locations are where the adhesive binder tends to fiow and then set. Also, abrasive particles are located along the lengths of the fibers at portions thereof other than where the fibers cross and contact one another.

Intermediate batt section 12 is formed from randomly arranged fibers 14 secured together by adhesive 15 at locations where the fibers cross and contact one another. Intermediate section 12 is completely impregnated with a detergent composition, indicated by cross hatching 17. Detergent 17 completely fills the voids between adjacent fibers 14, intermediate section 12 being substantially inflexible prior to use. Since intermediate section 12 is disposed where it will not contact work to be scoured, there is no need to have abrasive particles 16 applied to it.

A preferred method of producing a scouring article as illustrated in FIGS. l and 2 is to form each of sections 11, 12 and 13 separately and then laminate the sections together to form a unitary batt. Sections 11 and 13, which incorporate abrasive particles 16 therein, may be made in accordance with a method and by means apparatus described in copending U.S. application Serial No. 35,626, filed June 13, 1960 in the name of John A. Carneron. It may also be produced in acordance with the disclosure of U.S. Patent No. 2,958,593 to Hoover et al. Particles 16 may be sprayed on a batt surface alone or admixed with a resin binder. If it is desired to incorporate abrasive particles in intermediate batt section 12, this section, too, may be formed by the same methods and apparatus as sections 11 and 13. In the embodiment of FIGS. l and 2, however, abrasive particles are not incorporated in batt section 12, a resinous binder 15 being applied to the section without abrasive particles included therein. Once formed, batt section 12 is then completely impregnated with detergent 17 by an impregnating method and apparatus such as that described in said U.S. application Serial No. 35,626.

A modified form of scouring article is illustrated in FIG. 3 of the drawing. Scouring pad 20 is, like pad 10, composed of three separate batt sections 21, 22 and 23. Batt sections 21 and 22 are identical to sections 11 and 12 of the embodiment of FIGS. l and 2. Batt section 23 is similar to section 13 except that it has no abrasive particles as part of its structure. Instead, fibers 24 are adhered to each other by binder 25 at locations where those fibers cross and contact one another in the same manner as the fibers of batt sections 12 and 22; no abrasive particles are stationed along the lengths of the fibers 24 or at concentrations of binder 25, as is exemplified by abrasive particles 26 of batt section 21. Intermediate section 22 is impregnated with detergent 27 and the three sections of batt 20 are united in the same manner as the sections of batt 10 by any suitable means such as an adhesive.

The advantage which is obtained from a structure such as that of FIG. 3 as compared with the structure of FIGS. 1 and 2 is that the pad therein illustrated presents one highly abrasive and one less abrasive working surface. In household use, the highly abrasive surface of section 21 can be utilized to scour pans and the like, while the less abrasive surface of section 23 can be used to remove adhering particles from dishes and the like without scratching or otherwise marring the dishes. The same advantages with regard to metering of detergent 27 are present regardless of which surface of article 20 is presented to the work.

Various acids can be added to the detergent compositions to make a product more effective, for example, in removing oxides and sulfides from copper and brass articles.

Alternatively, high caustic levels can be introduced into the detergent system to make the product more effective in Working with carbonized greases and fats. Typical of the materials in the iirst category of acids are sulfamic, oxalic, phosphoric, and tartaric. A typical material in the second class (that is the alkali system) is sodium hydroxide. Also, combinations of these additives may be made to modify the cleaning properties of the detergent-impregnated articles. The level of such active addi- Vtives will vary in accordance with the cleaning problem required; for instance, where the Working surface is copper, the level of acidic components employed will be relatively high in comparison with the level of detergent required, whereas, in the removal of highly greasy and oilytype soils, the level of detergency must be high to ernulsify these greases and oils.

While the present invention has been described with particular reference to specific embodiment of the scouring article, and a method for the manufacture thereof, it will be understood that the invention is not to be limited by those embodiments, but the scope of the invention is to be determined only by reference to the following appended claims.

This application is filed as a continuation-in-part of my copending application Serial No. 35,626, led June 13, 1960 for w impregnated Scouring Article and Method and Apparatus for Making Same.

What is claimed is:

l. An abrasive, detergent-containing scouring article, comprising iirst and second lofty low density three-dimensional batt sections each of which is composed of a plurality of liexible tough organic fibers which are intermingled and disposed in random arrangement to form a network of intercornmunicating voids extending through said sections, said fibers being bonded together at spaced points where they cross and contact one another to unite each of said sections into an integral resilient structure throughout its dimensions, said rst section being substantially free of detergent and having a work contacting surface, said first and second sections being joined together at contiguous surfaces by an adhesive, said joined surface of said first section being a substantially planar surface other than said work contacting surface, said second section having impregnated in the voids of its network a detergent solid at room temperature and activatable in the presence of solvent to pass from said second section through said network of voids in said rst section to said work contacting surface.

2. An abrasive, detergent-containing scouring article, comprising three lofty low density three-dimensional batt sections each of which is composed of a plurality of ilexible tough organic fibers which are intermingled and disposed in random arrangement to form a network of intercommunicating voids extending through each of said sections, said fibers being bonded together at spaced points where they cross and contact one another to unite each of said sections into a separate integral resilient structure throughout its dimensions, said sections being juxtaposed and bonded together to form a unitary scouring article composed of two outer batt sections and an intermediate batt section positioned therebetween, each of said outer sections having a work contacting surface and said intermediate section being joined to said outer sections along surfaces thereof other than said work contacting surfaces, said intermediate section having impregnated in the voids of its network a detergent solid at room temperature and activatable in the presence of solvent to pass from said intermediate section through said network of voids in each of said outer sections to said work contacting surfaces.

3. An abrasive, detergent-containing scouring article, comprising three lofty low density three-dimensional batt sections each of which is composed of a plurality of flexible tough organic lfibers twhich are intermingled and disposed in random arrangement to form a network of intercommunicating voids extending through each of said ections, said iibens being bonded together at spaced points where they cross and contact one another to unite each of `said sections into a separate integral resilient structure throughout its dimensions, said sections being juxtaposed and bonded together to form a unitary scouring article composed of two outer batt sections and :an intermediate batt section positioned therebetween, each of said outer sections having a work contacting surface, abrasive particles distributed only on one of said work contacting surfaces and bonded to iibers orf said batt section at said surface, said intermediate batt section being joined to said outer sections along surfaces thereof other than said `work contacting surfaces and having impregnated in the voids of its network a detergent solid at room temperature and activatable in the presence of solvent to pass from said intermediate section through said networks of voids in said outer sec-tions to said work contacting surfaces.

4. An abrasive, detergent containing scouring article, comprising first and second lofty low density three dimensional batt sections each of which is composedof a plurality of -iiexible tough organic fibers which are intermingled and disposed in random arrangement to form a network of intercommunicating voids extending through said sections, said fibers being bonded together at spaced points where they cross and contact one another to unite each of said sections into lan integral resilient structure throughout its dimensions, said first section having a work-contactingV surface and a substantially planar surrface opposed to said work-contacting surface, said opposed surface having a continuous edge bounding said surface, said second section being joined to said first section at said opposed -surface by means of la substantially planar surface of said second section which is bounded by a continuous edge lthat is substantially congruent with said continuous edge of said opposed surface, said second section having stationed in the voids of its network a detergent solid at room temperature and activatable in the presence of solvent to pass from said second section through said network of voids in said irst section to said work-contacting surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,978,169 Ricketts Oct. 23, 1934 2,079,600 Brooks 4May 1l, 1937 2,958,593 Hoover et al. Nov. l, 1960 

4. AN ABRASIVE, DETERGENT CONTAINING SCOURING ARTICLE, COMPRISING FIRST AND SECOND LOFTY LOW DENSITY THREE DIMENSIONAL BATT SECTIONS EACH OF WHICH IS COMPOSED OF A PLURALITY OF FLEXIBLE TOUGH ORGANIC FIBERS WHICH ARE INTERMINGLED AND DISPOSED IN RANDOM ARRANGEMENT TO FORM A NETWORK OF INTERCOMMUNICATING VOIDS EXTENDING THROUGH SAID SECTIONS, SAID FIBERS BEING BONDED TOGETHER AT SPACED POINTS WHERE THEY CROSS AND CONTACT ONE ANOTHER TO UNITE EACH OF SAID SECTIONS INTO AN INTEGRAL RESILIENT STRUCTURE THROUGHOUT ITS DIMENSIONS, SAID FIRST SECTION HAVING A WORK-CONTACTING SURFACE AND A SUBSTANTIALLY PLANAR SURFACE OPPOSED TO SAID WORK-CONTACTING SURFACE, SAID OPPOSED SURFACE HAVING A CONTINUOUS EDGE BOUNDING SAID SURFACE, SAID SECOND SECTION BEING JOINED TO SAID FIRST SECTION AT SAID OPPOSED SURFACE BY MEANS OF A SUBSTANTIALLY PLANAR SURFACE OF SAID SECOND SECTION WHICH IS BOUNDED BY A CONTINUOUS EDGE THAT IS SUBSTANTIALLY CONGRUENT WITH SAID CONTINUOUS EDGE OF SAID OPPOSED SURFACE, SAID SECOND SECTION HAVING STATIONED IN THE VOIDS OF ITS NETWORK A DETERGENT SOLID AT ROOM TEMPERATURE AND ACTIVATABLE IN THE PRESENCE OF SOLVENT TO PASS FROM SAID SECOND SECTION THROUGH SAID NETWORK OF VOIDS IN SAID FIRST SECTION TO SAID WORK-CONTACTING SURFACE. 